In some cases, an ailment may affect a patient's sleep quality or physical activity level, or a therapy delivered to the patient to treat the ailment may produce undesirable side effects. For example, chronic pain may cause a patient to have difficulty falling asleep, and may disturb the patient's sleep, e.g., causing the patient to wake. Further, chronic pain may cause the patient to have difficulty achieving deeper sleep states, such as one of the nonrapid eye movement (NREM) sleep states associated with deeper sleep. Other ailments that may negatively affect patient sleep quality include movement disorders, such as tremor, Parkinson's disease, multiple sclerosis, epilepsy, or spasticity, as well as psychological disorders, such as depression, mania, bipolar disorder, or obsessive-compulsive disorder. Further, sleep apnea, congestive heart failure, gastrointestinal disorders and incontinence may negatively affect patient sleep quality. As another example, chronic pain may cause a patient to avoid particular physical activities, or activity in general, where such activities increase the pain experienced by the patient. Neurological disorders such as movement disorders and psychological disorders, in addition to congestive heart failure, may also affect patient activity level.
Furthermore, in some cases, poor sleep quality may increase the symptoms experienced by a patient due to an ailment. For example, poor sleep quality has been linked to increased pain symptoms in chronic pain patients, increased tremor or other inappropriate movements in movement disorder patients, and worsening of psychological symptoms. The link between poor sleep quality and increased symptoms is not limited to ailments that negatively impact sleep quality, such as those listed above. Nonetheless, the condition of a patient with such an ailment may progressively worsen when symptoms disturb sleep quality, which in turn increases the frequency and/or intensity of symptoms.
In some cases, these ailments are treated via a medical device, such as an implantable medical device (IMD). For example, patients may receive an implantable neurostimulator or drug delivery device to treat chronic pain or a movement disorder. Congestive heart failure may be treated by, for example, a cardiac pacemaker or drug delivery device.